This paper analyses a kinematic model for the solar motion by Quṭb al-Dīn al-Shīrāzī, a thirteenth-century Iranian astronomer at the Marāgha observatory in northwestern Iran. The purpose of this model is to account for the continuous decrease of the obliquity of the ecliptic and the solar eccentricity since the time of Ptolemy. Shīrāzī puts forward different versions of the model in his three major cosmographical works. In the final version, in his Tuḥfa, the mean ecliptic is defined by an eccentric (...) of fixed mean eccentricity and a mean obliquity fixed with respect to the celestial equator, and the center of the epicycle, which is inclined to the eccentric, moves on the eccentric with an annual period. By an additional slow motion of the sun on the epicycle, the true eccentricity of the solar deferent, defined by the annual motion of the sun, and the sun’s extreme declination from the equator change, accounting for the reduction of the eccentricity and the obliquity of the ecliptic since the time of Ptolemy. (shrink)

El manuscrito 2461 de la Biblioteca General de Rabat conserva un tercer zi)3 del astrónomo Muhammad ibn al-Raqqám al-Andalusí (m. 1315): al-Ziy al-Mustawfa. Los cánones (capitulo 18) y la tabla del movimiento del apogeo de al-Mustawfa están relacionados con el trabajo de Ibm Isháq al-Túnisí (1193-1222), quien compiló, probablemente, un conjunto de tablas carentes de cánones. Ibn al-Raqqám conocía bien el ziy de Ibn Isháq del que realizó dos recensiones conocidas hasta ahora: al-Ziy al- amil y al-Ziy al-Qawim. En al-Mustawfó, (...) tercera recensión de la misma obra, Ibn al-Raqqám aclara cuál era la opinión de Ibn Isl3áq sobre el movimiento de los apogeos planetarios y la división que existía, a este respecto, entre los astrónomos de la escuela andaluso-magrebí. (shrink)

Astronomers have always considered the motion of the Moon as highly complicated, and this motion is decisive in determining the circumstances of such critical celestial phenomena as eclipses. Table-makers devoted much ingenuity in trying to find ways to present it in tabular form. In the late Middle Ages, double argument tables provided a smart and compact solution to address this problem satisfactorily, and many tables of this kind were compiled by both Christian and Jewish astronomers. This paper presents multiple examples (...) of the diversity of approaches adopted by compilers of tables who used this powerful tool, and brings to light intellectual interactions among them that are otherwise hidden from view. (shrink)

During the Middle Ages Aristotle’s treatises were accessible to intellectuals via translations and commentaries. Among his works on natural philosophy, the zoological books received relatively little scholarly attention, though several medieval commentators carefully studied Aristotle’s investigations of the animal kingdom. Averroes completed in 1169 a commentary on an Arabic translation of Aristotle’s Parts of Animals and Generation of Animals. In 1323 Gersonides completed his supercommentary on a Hebrew translation of Averroes’ commentary. This article examines how these two medieval commentators interpret (...) the first book of Aristotle’s Parts of Animals, at the center of which stand methodological questions regarding the study of animals. Aristotle’s discussion of classification is presented by Averroes and Gersonides in light of an epistemological debate concerning the requisite method for scientific inquiries and discoveries. Sense perception is contrasted with rational reasoning, and ultimately a combined method is proposed, sense perception maintaining supremacy. These commentators outline a clear link between the systematic arrangement of animal species as offered by Aristotle, and his subsequent logical demonstrations which, according to them, form the core of biological investigations. (shrink)